R Plasmids with Thermosensitive Transferability in Salmonella Strains Isolated from Humans

Abstract

Temperature dependence of transfer was examined with ten R plasmids originating from clinical isolates of Salmonella. Six of the plasmids were thermosensitive upon transfer, five of which were originally harbored in S. typhimurium and the remaining one in S. derby. One of these plasmids, pNR502, which conferred resistance to kanamycin, streptomycin (Sm) and tetracycline (Tc) on its host was stably maintained both in Salmonella and Escherichia coli at either 30, 37, or 43 C. Another plasmid, pNR516, which was resistant to chloramphenicol, sulfathiazole, Sm and Tc, was slightly unstable only at 43 C. The remaining four plasmids, pNR503, pNR510, pNR512 and pNR514, conferred resistance to Sm and Tc. Of these plasmids, the former two were stably maintained at both 30 and 37 C, but were unstable at 43 C. The latter two were slightly unstable at the lower temperatures and considerably unstable at 43 C. Kinetics of the transfer of the plasmid pNR503 revealed that the efficiency of transfer of the plasmid between E. coli strains was affected not only by the temperature of the conjugation but also by the preincubation temperature of the donor culture before the conjugation.Several reports have already shown that many R plasmids exhibited thermosensitivity upon transfer in bacterial conjugation. Most of them were more or less unstably maintained at high temperatures except the plasmids isolated from Vibrio cholerae (12) and Serratia marcescens (6). Particularly in Salmonella (2, 8, 9), the plasmids with thermosensitive conjugational transfer have frequently been isolated. We have also reported the occurrence of an R plasmid with temperature-sensitive transferability in S. typhimurium (13).In this report, we have studied whether the temperature-sensitivity of transfer of the R plasmids isolated from Salmonella is a common phenomenon. For this purpose, ten R+ Salmonella strains were examined for transferability at 30 C as well as at 37 C. The kinetics of conjugational transfer of an R plasmid was studied to clarify the effects of the temperature of cultivation upon transfer.

Effect of donor-recipient relatedness on the plasmid conjugation frequency: a meta-analysis

“…Our selection for studies which mentioned more than one recipient species in the abstract, used liquid broth matings or filter matings with E. coli donors containing a self-transmissible plasmid yielded 32 studies ( Fig. 1) reporting 313 conjugation frequencies for liquid broth matings [9,[35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] and 270 conjugation frequencies for filter matings [38,44,45,50,[52][53][54][55][56][57][58][59][60][61][62][63][64][65].…”